Vessel with active mechanism for controlled towing

ABSTRACT

A vessel for towing a towed body in or on a body of water is disclosed. The vessel includes a vessel, a tow arm mechanism carried by the vessel, a towed body linked to the tow arm mechanism, and at least one sensor carried by either the vessel or the towed body. The sensor generates sensor data, and a towing mechanism controller receives the sensor data and positionally adjusts the tow arm mechanism based on the data.

TECHNICAL FIELD

Generally, the present invention relates to vessels that tow sensors.Specifically, the present invention is directed to vessels that towsensors with a towing arm that has an end that is movable so as tominimally offset a towline force vector from the vessel's center ofgravity. In particular, the present invention is directed to vesselsthat tow sensors wherein the vessel and/or towed body is provided with amotion and position sensor to detect changes in the towline force vectorso as to actively move the towing arm to compensate for those changes.

BACKGROUND

Various types of sensors are utilized for evaluations of bodies ofwater. These sensors can be used for seismic surveys, sea floor mapping,and environmental and coastal surface surveys. These sensors can also beused to detect underwater conditions for military purposes such as forsurveillance, the detection of mines and/or other submerged vehicles.

One method is to tow a sensor from an aircraft such as a helicopter oran appropriate vessel. Towing sensors from surface vessels provide a lowcost advantage over an airborne-towed sensor. Vessels that tow sensorsare fairly easily deployed, can be remotely controlled and are easilyretrieved for review of the detected information.

Although use of towed sensors is advantageous, use of a vessel to tow asensor has certain drawbacks. It is known that small craft used to towsensors have difficulty in controlling the impact of the towing vessel'smotions on a towed sensor and also conversely, the impact of the towedsensor's forces on the attitude of the towing craft are encountered. Inprior art small craft monohull vessels, a transom winch on an A-framemounted on the stern is used to place a tow point above and behind thevessel. This tow point location away from the vessel's center of gravityallows vessel pitch motion to be transmitted to the tow line tension andthis results in unwanted sensor motion. And the distance of the towpoint from the vessel's center of gravity and the resulting couplemotions of pitch and heave, and towing from an A-frame also imposeshigher forces on the towed body, thereby degrading its motionperformance. Towing from an A-frame also creates a pitching motion ormoment on the towing vessel, due to the towing force vector offset abovethe thrust line of the towing vessel's propulsors. It also generates aforce vector significantly away from the towing vessel's center ofgravity, thereby imposing moments that are deleterious to the vessel'sperformance. Moreover, the tension from the drag of the sensor and towline, in turn, adds to the vessel trim and roll angles. Vesselmaneuvering and the resulting off-axis forces also add a yaw moment.Adding trim to a vessel adds to its resistance. Adding roll and yawmoment to a vessel impacts on-board equipment performance and hindersthe ability to control the vessel. Minimizing the towing forces on thetowed body also becomes critical particularly as the size of the vesselbecomes small relative to the size of the towed body. In addition, thesensor is exposed to transverse currents, waves and wind forces whichfurther contribute to the deleterious forces imparted on the vessel.These forces also provide extra wear on the tether connecting the vesselto the towed sensor.

In summary, prior art small craft vessels that tow a sensor usually doso from a non-optimal fixed point and such small craft have no way ofadjusting the fixed point to accommodate operational characteristic ofthe vessel or environmental characteristics that are encountered whiletowing the sensor. Indeed, a towed sensor that is exposed to extraneousforces interferes with the main purpose of the sensor in collectingdata. In other words, if a sensor is not maintained in a steady anduniform path, its ability to collect data regarding mine positions ormapping of sea floor characteristics is significantly reduced.

Therefore, there is a need in the art for a vessel that tows a sensor ortowed body wherein a tow arm mechanism is actively maintained tominimize deleterious forces on the vessel and the towed body. There isalso a need to provide a tow arm mechanism that controls the tow linetensile vector by a mechanism that allows the vector to be directedthrough an optimum point in relation to the towing craft. Moreover,there is a need for vectoring the force through the center of gravity ofthe vessel so as to eliminate the induced trim, roll and yaw moments. Byvectoring the force through the thrust line of the propulsion of thevessel, such a configuration eliminates the induced trim of the vesseland allows it to operate more efficiently. And there is a need in theart for controlling the tow line tensile vector when the ratio of towforce to vessel displacement becomes large. There is also a need toprovide sensors on board the vessel and the towed body to providepositional and motion input that is processed and delivered to acontroller for the tow arm mechanism.

SUMMARY OF THE INVENTION

In light of the foregoing, it is a first aspect of the present inventionto provide a vessel with active mechanism for controlled towing.

It is another aspect of the present invention to provide a vessel fortowing a towed body in or on a body of water, comprising a vessel, a towarm mechanism carried by the vessel, a towed body linked to the tow armmechanism, at least one sensor carried by either the vessel or the towedbody, the at least one sensor generating sensor data, and a towingmechanism controller receiving the sensor data and positionallyadjusting the tow arm mechanism based on the data.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention willbecome better understood with regard to the following description,appended claims, and accompanying drawings wherein:

FIG. 1 is a rear side perspective view of a vessel with an activemechanism for controlled towing according to the present inventionshowing a towed body in a retained position;

FIG. 2 is a rear perspective view of the vessel according to the presentinvention with the towed body shown in a deployed position;

FIG. 3 is an elevational view, partially broken away, of the vesselaccording to the present invention showing a tow arm mechanism invarious operational positions; and

FIG. 4 is a schematic diagram of a tow arm control system employed bythe vessel according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring now to the drawings and particularly to FIGS. 1-3, it can beseen that a vessel with an active mechanism and a controlled towingsystem is designated generally by the numeral 10. The system 10 includesa vessel 12 which may be any kind of water-borne craft. In mostembodiments of the present invention the craft is a relatively smallmotorized craft, but the concepts of the present invention can beemployed with any type of towing vessel. The vessel 12 carries a vesselposition and motion sensor 14 which monitors the position speed, pitch,yaw, roll and other operational characteristics of the vessel. The datacollected by the sensor 14 is transmitted via a data line 16. In someembodiments the sensor 14 may wirelessly transmit data associated withor collected by the sensor 14. The vessel 12 includes a cabin 18 whichhouses various instruments and control systems for operating the vessel12. In some embodiments the cabin may accommodate personnel and in otherembodiments the cabin may be configured for remote control from otherships, or land-based or air-based control systems.

A tow mechanism controller 20 is maintained by the vessel and mostlikely maintained within the cabin 18. Generally, the tow mechanismcontroller 20 receives data, such as sensor information from data line16 and generates control signals 22. The control signals 22 may compriseany number of control signals needed to implement the objects of theinvention.

The vessel 12 is a multi-hull vessel and, as such, provides a starboardhull 24 and a port hull 26. The spacing between the hulls 24, 26 form amoonpool-like opening 28 therebetween. Although the present inventioncan be employed with any type of water-borne craft as described above,it is believed that a dual hull configuration as shown and describedherein provides a number of additional benefits that will be discussed.In any event, the starboard hull 24 maintains a starboard propulsor 30and, in a similar manner, the port hull 26 maintains a port propulsor32. In the alternative, the hulls may carry other means for propulsion,such as propellers and the like. Each propulsor 30/32 has associatedtherewith a thrust sensor 33. Each thrust sensor 33 measures the currentpropulsor thrust and generates propulsor data 34 that is sent ortransmitted to the tow mechanism controller 20.

A tow arm mechanism is designated generally by the numeral 50 andmounted proximal the cabin 18 and fore of a cradle 51. The tow armmechanism carries a towed body 52 such as SONAR or other type of sensorutilized to observe a phenomenon or feature maintained in the body ofwater under examination. The cradle 51, as shown in FIG. 1, carries thetowed body 52 as the vessel moves to the area to be surveyed. As seen inFIG. 2, the cradle 51 is lowered at one end to deploy the towed body 52.Data collected by the towed body may be stored for later retrieval ortransmitted to an appropriate receiver. The towed body 52 includes atowed body position and motion sensor 54 which generates motion data 56that is transmitted to the tow mechanism controller 20. In much the samemanner as the vessel position and motion sensor 14, the towed bodyposition and motion sensor 54 generates information related to theforces applied to the towed body during deployment and operation of thevessel 12. In other words, as the towed body 52 is pulled by the vessel12, the body 52 experiences any number of forces that are detected bythe sensor 54 and transmitted to the controller 20 for processing.

The tow arm mechanism 50 includes a pair of opposed buttress plates 60wherein each plate 60 is carried by the vessel on each side of themoonpool opening. The buttress plates 60 carry the tow arm mechanism 50and related components as will be described below. Carried between thebuttress plates 60 is a winch 62 which comprises a rotatable cylindricaldrum. An arm 64, which is pivotable in various directions, is carried bythe vessel and mounted between the buttress plates 60. A tow line 66 iscarried by the winch and wound around its cylindrical drum. The tow line66 interconnects the towed body 52 to the vessel 12. The tow line 66 isconstructed of a strong flexible material which may simply carry thetowed body or in some embodiments may incorporate communication cablesto as to transmit information between the vessel and the towed body. Insome embodiments, the data may be transmitted wirelessly from the towedbody to the vessel or transmitted to other ships located in the area ofthe vessel 12. The tow line 66 may also be directly connected to the towmechanism controller 20 such that information data 56 transmitted by thetowed body position and motion sensor 54 provides real-time informationto the controller 20.

A winch motor 68 is coupled to the winch 62 and reels the tow line 66 inand pays it out as needed. The winch motor 68 receives a winch motorcontrol signal 70 from the tow mechanism controller 20. A winch motorsensor 72 is coupled to the winch motor 68 and detects torque forcesapplied to the tow line during deployment and operation. The sensor 72generates winch motor data 74 which is transmitted to the tow mechanismcontroller 20. The tow line 66 is also monitored by a tow line quantitysensor 76 mounted proximally to the winch 62 so as to detect the lengthof the tow line deployed during operation. The quantity sensor generatesa data signal 77 which is transmitted to the tow mechanism controller20.

A tow arm axle 80 is mounted between the buttress plates 60 and isrotatable by a tow arm axis motor 82 which rotates the axle. The arm 64is secured to the axle 80 and, as a result, the tow arm 64 is movableinto the desired angular positions. In an alternative embodiment, theaxle 80 could be fixed to the plates 60 and the arm 64 pivots withrespect to the axis. Other interconnections between the tow arm 64 andthe axle 80 and/or vessel 12 could be employed. Examples of the variouspositions can best be seen in FIG. 3. The tow arm axis motor 82 receivesa tow arm control signal 84 from the tow mechanism controller so as toadjust the angular position of the tow arm as needed. A tow arm sensor86 is coupled to the axle 80 so as to detect the rotational position ofthe axle and, as such, the angular position of the tow arm. The sensor86 generates axis data 88 which is sent to the tow arm controller 20 formonitoring of the tow arm position and adjustments as needed.

Included in the tow arm mechanism 50 is a lateral mover 90 which may bemounted on the tow arm axle 80. The mover 90 moves the arm 64 side toside along the length of the axle 80 based upon a lateral mover controlsignal 92 generated by the tow mechanism controller 20. In order toensure proper operation of the lateral mover 98, a lateral mover sensor94 may be associated therewith and generates lateral mover data 96 thatis transmitted to the controller 20. In some embodiments, lateralmovement of the arm 64 may be obtained by moving the buttress plates 60or some other mechanical configuration as deemed appropriate.

The arm 64 includes a pair of flanges 102 spaced apart from each otherand are of a generally similar construction. The arm 64 includes an axleend 104 which is mounted upon the tow arm axle 80. At an end oppositethe axle end 104, the flanges 102 provide an elbow 106. Angularlyextending from the elbow 106 is a hook end 108 which terminates theflanges 102. The flanges 102 are separated but connected to one anotherby a number of sheaves. Specifically, an axle sheave 110 is maintainednear or on the axle end 104. Indeed, the axle sheave 110 is mounted onthe axle 80 and separates the flanges 102 from one another. An elbowsheave 112 is maintained at the elbow 106 and a hook sheave 114 ismaintained at the hook end 108. As skilled artisans will appreciate, thesheaves 110/112/114 are rotatable members with a grooved central portionwhich accommodates the diameter of the tow line 66. Together, the elbowsheave 112, the hook sheave 114 and the flanges 102 form a tow lineopening 116 such that the outer diameter of the tow line fits within andeasily moves along the respective grooves and is routed or threadedbetween and through the opening 116 so as to direct movement of the towline and the towed body. As best seen in FIG. 3, when the tow arm is inan upward angular position, such as when the towed body is in a retainedposition, the tow line is primarily supported by the elbow sheave 112.As the arm 64 is lowered into a position to deploy the towed body, thetow line is supported by the axle sheave 110, the elbow sheave 112 andhook sheave 114. In some instances the hook end 108 may be loweredbeneath the water line supporting the vessel 12 and as a result the towline is primarily directed by the hook sheave 114 and supported by theelbow sheave 112 and axle sheave 110.

In some embodiments, a hook sheave sensor 118 may be mounted to the hooksheave 114 and generates sensor data 120 that is transmitted to the towmechanism controller 20. The hook sheave sensor determines a magnitudevector of the tow force and forces applied to the tow line 66.

As best seen in FIG. 3, the vessel provides a propulsor level base line122 which is essentially the water line that supports the vessel 12. Thevessel also provides a center of gravity 124 which is used to referencethe position of the tow arm as will be described.

Overall operation of the tow arm mechanism 50 is maintained by a tow armcontrol system designated generally by the numeral 126 as shown in FIG.4. User input 128 is provided to the control system 126 and specificallyto the tow mechanism controller 20. User input 128 may also be providedto the propulsors 30/32 so as to control the speed of the vessel and, itwill also be appreciated that user input is provided to a steeringmechanism that controls the maneuverability and direction of the vessel.Along with receiving user input, the tow mechanism controller 20receives position and motion data 16/56 from the sensors 14 and 54 whichdirectly monitor the forces being applied to the towed body and thevessel. Other inputs received by the tow mechanism controller includethe data related to the thrust sensors 33, the hook sheave sensor 118,the tow line quantity sensor 76, the tow arm sensor 86, the lateralsensor 94 and the winch sensor 72. Based upon these various inputs thatthe tow mechanism controller receives, which monitor the operation ofthe tow mechanism, the vessel 12 and the towed body, the tow mechanismgenerates control signals 22 -- such as the tow arm axis motor signal84, the lateral mover motor signal 92, and the winch motor signal 70 --so as to adjust the position of the tow arm and provide for improvedoperation of the towed body and the vessel. In other words, as variousforces impact the towed body and the vessel, the controller selectivelyadjusts the angular position of the arm, the lateral position of the armand/or the tension force applied by the winch motor to the tow line. Forexample, as the vessel begins a turning maneuver, the vessel sensor 14and the towed body sensor 54 detect the various changes in forcesapplied to the towed body and the sensor. The controller 20 receivesthese changes and generates control signals 22 to adjust the componentforces exerted on the tow line by the tow arm axis motor 82, the lateralmover motor 90 and/or the winch motor 68. Forces detected by the othersensors 118, 76, 86, 94, 72 and 33 can also be used to determine theextent and nature of the control signals generated. As the controller 20and the system 126 gain experience, the control signals can becollectively generated to provide for optimum operation of the vessel 12and/or optimum data collection for the towed body. As a result, thecontroller 20 provides enhanced control during normal running conditionsincluding maneuvers.

By utilizing the control system 126, operation of the controller 20actively controls the arm 64 in both the vertical and lateral planesrelative to the vessel 12. For example, with the object being towed viathe tow line, the end of the tow arm is controlled, which allows thevector of the towline tensile force to be controlled. Controlling thetowline tensile vector allows the force to be extrapolated through thecenter of gravity of the vessel, the thrust vector or some other optimumpoint of the tow vessel. The tow point can be therefore controlled viathe controller 20 or with the assistance of a human or automated controlsystem, or remotely operated by a link associated with the vessel orsome combination thereof to actively control the inter relationshipbetween the towed object and the towing vessel.

Utilization of system 10 with the control system 126 which incorporatesthe controller 20 provides a number of advantages. First, towing a bodyfrom a multi hull vessel provides greater flexibility for controllingthe tow point to reduce deleterious effects through the opening 28between the multiple hulls both laterally and longitudinally on thecraft. In other words, by utilizing an active mechanism for controllingthe position of the tow vector, it will be appreciated that its path ispositionable through or very close to the center of gravity of thevessel, or through the thrust vector of the propulsor or some optimalposition of compromise between the two. Still other advantages arerealized in that towing of a towed body 52 in areas of high sea statesdictates a preference for the towing vessel to be a multi hullconfiguration due to its superior sea keeping and sea-kindliness. Thisimproved sea keeping reduces the towing vessel's motion which, in turn,reduces the imposed motions on the towed body. Improved sea keeping alsoimproves the effectiveness of the controlling and gathering ofinformation from the towed body in the case of a manned vessel, orimproves the ability to control through improved remote sensingcapabilities in case of an unmanned tow vessel. Additionally, use ofmulti hulls allows for faster transit time to the area of interest forthe sensor in tow.

Other advantages are realized by actively controlling the tow pointposition in space minimized the induced motion on the towed body andtowing vessel. As a result, the tow line can be controlled at anelevation so that the tow line does not contact the hull or propulsorswhich in turn increases the life and reliability of the tow line. Stillanother advantage is that controlling the tow force vector through thetowing vessel propulsor thrust line reduces induced hull drag andminimizes the size of the propulsion motors, particularly when thetowing vessel size is smaller in proportion to the size of the towedobjects.

Thus, it can be seen that the objects of the invention have beensatisfied by the structure and its method for use presented above. Whilein accordance with the Patent Statutes, only the best mode and preferredembodiment has been presented and described in detail, it is to beunderstood that the invention is not limited thereto or thereby.Accordingly, for an appreciation of the true scope and breadth of theinvention, reference should be made to the following claims.

1. A vessel for towing a towed body in or on a body of water,comprising: a vessel; a tow arm mechanism carried by said vessel; atowed body linked to said tow arm mechanism; at least one sensor carriedby either said vessel or said towed body, said at least one sensorgenerating sensor data; and a towing mechanism controller receiving saidsensor data and positionally adjusting said tow arm mechanism based onsaid data.
 2. The vessel according to claim 1, wherein said tow armmechanism comprises: a winch which carries a tow line, wherein one endof said tow line is connected to said towed body; and an arm pivotablycarried by said vessel, wherein said arm moves said tow line to aposition proximal in line with said vessel's center of gravity.
 3. Thevessel according to claim 2, wherein said towing mechanism controlleradjusts a position of said arm based on said sensor data.
 4. The vesselaccording to claim 3, wherein said tow arm mechanism further comprises:an opposed pair of buttress places, wherein said winch is mountedbetween said buttress plates; a frame axle mounted between said buttressplates, wherein one end of said arm is mounted on said axle; and an axlemotor rotatably moving said frame axle so as to pivotably move said arm,said axle motor receiving an axle control signal from said towingmechanism controller to pivotably move said arm based on data from saidat least one sensor received by said towing mechanism controller.
 5. Thevessel according to claim 4, further comprising: an axle sensor coupledto said frame axle to detect an angular position and send said angularposition to said towing mechanism controller.
 6. The vessel according toclaim 4, wherein said tow arm mechanism further comprises: a lateralmover motor laterally moving said arm, said lateral mover motorreceiving a lateral mover control signal from said towing mechanismcontroller to laterally move said arm in relation to said axle based ondata from said at least one sensor received by said towing mechanismcontroller.
 7. The vessel according to claim 4, wherein said tow armmechanism further comprises: a winch motor coupled to said winch to payout and reel in said tow line, said winch motor receiving a winchcontrol signal from said towing mechanism controller to adjust tensionon said tow line based on data from said at least one sensor received bysaid towing mechanism controller.
 8. The vessel according to claim 4,wherein said vessel comprises a starboard hull and a port hull spacedapart from one another and forming a moonpool opening therebetween, eachsaid hull having a propulsor associated therewith, and wherein said armhas an end opposite said axle that is extendable into said moonpoolopening.
 9. The vessel according to claim 8, further comprising: athrust sensor associated with each said propulsor, said thrust sensordetecting thrust forces generated by said propulsors and sendingpropulsor data to said towing mechanism controller.
 10. The vesselaccording to claim 4, wherein said towed body carries a motion andposition sensor that sends motion data to said towing mechanismcontroller.
 11. The vessel according to claim 10, wherein said motionand position data is sent along said tow line.
 12. The vessel accordingto claim 4, wherein said arm comprises a pair of spaced apart flangeseach having an axle end rotatably mounted on said frame axle, each saidflange extending from said axle end to an elbow from which angularlyextends a hook end.
 13. The vessel according to claim 12, furthercomprising a plurality of sheaves disposed between said flanges at saidaxle end, said elbow and said hook end and guiding said tow line as saidarm pivots to different angular positions.